1. Field of the Invention
The present invention relates generally to medical leads, and more particularly to implantable medical leads having conductive materials deposited within the lumen of the lead body.
2. Description of the Related Art
Implantable leads form an electrical connection between a pulse generator or other electronic device and a tissue or structure in the body. For example, leads transmit electric signals used to stimulate cardiac or nerve tissue in one direction and signals generated by sensors placed in proximity to particular organs or tissues in the opposite direction. Leads typically include one or more electric elements at the lead""s distal end. The electric elements are designed to form an electrical connection with a tissue or organ. Most leads also include a lead connector pin at the lead""s proximal end. Lead connector pins are adapted to electrically and mechanically connect leads to the pulse generators or other electronic medical devices. A conductor connects the electric element to the lead connector pin. Commonly, the conductor takes the form of a single or multifilar wire coil. Stranded cable conductors are also common. Regardless of the conductors form, an insulating layer of material typically surrounds the conductors. Together, the flexible conductor and the insulating layer form the lead body.
Lead bodies having coils or cables can suffer from a variety of disadvantages, including fractured coils/cables, coil corrosion, difficult assembly, limited flexibility, and size limitations among others. Flex fatigue is a particularly prevalent problem. Flex fatigue is the fatiguing of the conductors upon repeated flexing caused, for example, by the pumping of the heart. Flex fatigue can lead to the fracture of one or more conductors reducing or eliminating the lead""s conductivity. This problem is exacerbated as coils are reduced in size. Closely related to fatigue is clavicle crush. Clavicle crush is the crushing of a lead implanted through the subclavian vein by the clavicle. The crushing can cause fracture of the conductors. Because of the need to access the heart through the subclavian vein, there is a need for a lead body more resistant to clavicle crush. Hence, a need exists for a lead that is more resistant to fracture due to flex fatigue, clavicle crush and other stresses that will be recognized by those skilled in the art.
The coils or cables also limit the minimum size for a lead body. Smaller diameter leads allow the placement of leads in more restricted spaces, such as cardiac veins or the epidural space, with a reduced affect on the patient relative to current lead sizes. Further, a smaller lead allows the use of smaller introducers that reduce the trauma associated with implantation. Similarly, a smaller removal sheath may also be used when explanting the reduced diameter lead. Hence, there exists a need to reduce the diameter of the lead bodies.
In addition, manufacturing leads is costly. Forming a secure electrical junction between the conductors and electric elements has proven difficult and time consuming. Laser welds are commonly used to connect the conductors to electric elements. Laser welding the coils to electric elements typically requires that the end of a coil be ground flat. Grinding the ends flat allows sufficient contact between the coil and the electrical element to weld the two together with a butt joint. Grinding increases the time, complexity and cost of manufacture. Further, welding may require the synchronized rotation of the conductor and electric element to weld at the various points around their circumference. The rotating also adds to the time, complexity and costs of manufacture. Alternatively, ring electrodes are connected to a conductor by etching away a region of insulator, applying a coating of electrically conductive adhesive, and then placing the ring electrode around the conductor. This method is also time consuming and expensive. Certain electrodes can also be crimped to the coiled or stranded conductor. Crimping, while a relatively simple process, places restrictions on the lead""s design. Further, crimping is relatively time consuming and can add significantly to the products cost. Hence, there exists a need to improve the manufacturing techniques used to secure electric elements to conductors in leads to reduce the time, complexity and cost.
The present invention meets these needs and provides other advantages and improvements that will be evident to those skilled in the art upon review of the following figures and description.
The present invention provides a lead body having an electrically conductive coating deposited within its lumen. The lead body is more flexible than leads employing coils or cables and offers the advantage of increased fatigue life while decreasing susceptibility to damaging in vivo forces, such as clavicle crush. The present invention reduces the cost in time and materials for the manufacture of the lead body relative to lead bodies employing coils or cables as conductors. The costs are reduced by, inter alia, eliminating various processes and related equipment required to join the coil or cable to other electrical components such as distal electrodes or the terminal components. The lead body may be manufactured in smaller sizes and with greater flexibility than with current methods of manufacture. The conductive coating occupying only minimal space in the lead body compared to typical coils and cables facilitates this reduction in size. In addition, the lead body allows for a simplified electrical connection between the lead body and the associated electrodes and/or sensors further reducing the cost of manufacture. Further, the present invention provides a lead that may realize the above and other advantages while providing handling characteristic similar to that of current lead designs, if desired by the user.
A lead body in accordance with the present invention includes a body defining at least one lumen, the lumen having a lumen wall. A conductive material is deposited on the lumen wall to conduct an electric current. When there are a plurality of lumen, at least one lumen is coated with a conductive material. The conductive material may be substantially coextensive or coextensive with the wall of the lumen. The lumen may be any of a number of shapes such as round, oval, triangle, square, pentagon, hexagon, heptagon, octagon or other shapes. The lead body may further include a protective layer covering the conductive material. The protective layer may impart desired performance characteristics on the lead body, protect the conductive layer, or both impart performance characteristic and protect the conductive layer.
In another embodiment, the lead body may include an inner body received within a lumen of an outer body. The inner body defines a lumen, the lumen having a lumen wall. The inner body may have a conductive material deposited on its lumen wall to conduct an electric current. Additional inner bodies may be provided to fit within the body. Each of the plurality of bodies defining a lumen, each lumen having a wall, and a conductive material deposited on the walls of at least one of the bodies to conduct an electric current. The plurality of inner bodies are received within the lumen of the body. The additional inner bodies may have different outside diameters and lumen diameters. The outside and lumen diameters corresponding such that in descending order of size each smaller body is fitted within the lumen of the next larger body.
A lead in accordance with the present invention is manufactured by providing a lead body defining a lumen and depositing a conductive material on a wall of the lumen. The conductive material may be deposited by electroless deposition, plasma deposition, sputtering, chemical deposition or other methods that will be recognized by those skilled in the art.
Electric elements, such as electrodes and sensors, may be secured to a lead body by fitting a sleeve of the electrical element within the lead body""s lumen to form an electrical contact between the electrical element and a conductive material. Further, electric elements may be secured to a lead body having an inner body and an outer body by fitting a sleeve of the electrical element between the inner body and the outer body to form an electrical contact between the electrical element and the conductive material. An adhesive that may itself be conductive may also be included to secure the sleeve within the lumen or between the bodies. Alternatively, the sleeve may be compressionally fit within the lumen or between the bodies. Again, an adhesive that may itself be conductive may also be included to secure the compressionally fit sleeve within the lumen or between the bodies.